Method, apparatus and system for transmitting and receiving client signals

The present invention provides a method, apparatus and system for transmitting and receiving a client signal. A client signal is mapped to a low-order ODU via a GFP scheme, wherein the low-order ODU is sized to M equal sized timeslots of a high-order OPUk, wherein the high-order OPUk is divided into N equal sized timeslots, wherein M is any one of a group from 1 to N; wherein if k=2, then N=8, if k=3, then N=32 and if k=4, then N=80. The low-order ODU with the client signal is mapped to M equal sized timeslots of the high-order OPUk via a GMP scheme; and an OTU with the high-order OPUk and overheads is formed, and then the OTU is transmitted.